This invention relates to a cam action, adjustable rod bender for surgical rods, more specifically, to a rod bender with a rotatable eccentric bending knob which rotates to one of a plurality of radius bend positions of use for insertion of a surgical rod between the rotatable knob and two fulcrums at the tops of each of the two handles, against which the rod is bent. When not in use, the cam rotates to alternate positions of radius bends.
Various attempts have been made to provide a rod bender for surgical rods, such as the French Rod Bender model no. KM 46-664 of the assignee K Medic, Inc. of Leonia, N.J. 07605 of the Applicant herein. While the prior art rod benders perform the same function of bending surgical rods about a circumferential recess of the knob, they have a fixed center cam which only allows the rod to be bent to a single radius. In contrast, the present rod bender includes an adjustable cam with three positions for three different radius bends.
The prior art does not disclose a cam action, rotatable movement of a movable bending knob for bending surgical rods into one of three desired radius bends by means of a locking cam bending knob, which knob is also retractable, outward away from a hinge about which two handles rotate, so that the knob can be rotated to one of a plurality of positions, such as three positions. In order to bend different sized rods, a separate device known as a reduction ring must be placed over the center knob of instrument. The disadvantages of the reduction ring are: 1) it is not part of the instrument and can become separated and lost 2) it is difficult to use 3) it can be hard to remove after use.
In contrast, the present invention provides a unique knee lever configuration which keeps the bending knob still while both handles are moved. The knee lever configuration includes two movable arms joined at a pinned joint, wherein a pin is slightly movable within a channel of a plurality of channels on a rear face of a round plate against which the bending knob is rotatably moveable to one of three desired positions. The pin slides within each channel, when the direction of the bending knob rotates 120 degrees to a desired locking position, against the round plate.
The knob is retracted outward, which outward movement is limited by an internal coil spring normally holding the knob in place against the round support plate.
Furthermore, for convenience another feature of the bending knob is found in that the bending knob includes equally spaced radius indentations to provide a good grip for the surgeon's hand while indexing.
Previous attempts to provide a surgical rod bender have provided an unadjustable assembly wherein a bending knob is provided at the hinge of two outwardly movable handles, which handles are each provided with bending surfaces. The rod is conditionally bent between the bending knob and the two bending surfaces. This unadjustable feature is undesirable, since it cannot adjust to varying radius bends, resulting in restrictions in the bending configuration of the surgical rods.
Furthermore, the prior art surgical rod bender do not describe an adjustable smooth cam acting rod bender with a locking bending knob which moves in a rotatable manner around a cam follower plate as the present invention provides.
The present invention improves upon the prior art by providing not only a cam action surgical rod bender assembly, but also a locking assembly which locks the knob in place when not in use. The present invention provides stability by the knee lever configuration for keeping the bending knob still, wherein a pin is moved downwardly along a channelled cam surface to provide stability when locking the bending knob in place against the round support plate at the hinge portion of the rod bender assembly.